Castiel’s body, possessed by the Leviathans and leaking black ooze, walks over to Dean, who calls to the unconscious Bobby. As Bobby wakes up, Dean distracts the Leviathans and says that the host body will soon explode. The Leviathans say that they’ll be back for Dean and stagger out of Crowley’s lab, unaware that down the hallway, Sam is struggling with Lucifer. Lucifer tells Sam that the two of them are real, but everything else is a hallucination and Sam is still in the cage in Hell.
Dean and Bobby arrive and Sam snaps out of his hallucination for the moment. They go after the Leviathans. Meanwhile, the Leviathans move Castiel’s vessel into a nearby municipal water supply. As the brothers and Bobby arrive, they watch Castiel’s body sink beneath the surface. A black vortex of liquid spreads out and the trio realizes that the water feeds into the public supply. Dean finds Castiel’s discarded trenchcoat and they figure that then angel is gone for good.
Across the area, people use the water. A young girl, Annie, drinks from a water fountain, shakes, and then smiles. A mechanic, Edgar, notices his sink vibrating. When he examines it, black fluid explodes out of the faucet and sprays in his face.
Sam is trying to sleep and hears Lucifer’s voice in his head. Dean wakes him up and offers him some water, and Sam takes it with his injured hand. While Dean checks on it, Lucifer sits nearby and mocks Dean’s efforts. Bobby hasn’t got any leads but figures the Leviathans will go public soon enough. Dean insists on talking about Sam’s situation, and Sam explains that he’s having trouble figuring out what’s real. He insists that he didn’t talk about it with them because they had enough going on, but admits that it’s getting more specific and he’s seeing Lucifer. When Dean points out that it doesn’t make sense for Lucifer to create a life for Sam, Sam and the hallucinatory Lucifer explain that there has to be something to take away from Sam for it to be torture. It’s a post-apocalyptic mess because it wouldn’t seem like Sam’s life if it wasn’t a mess. Dean realizes that Sam is seeing Lucifer and reminds him that it’s not real, but Sam points out that Lucifer is saying the same thing about Dean.
The possessed Annie is watching TV and tunes into an ad for Dr. Sexy M.D.
A character on the show sarcastically talks about doctors cutting into whoever they want.
At Bobby’s place, Sam silently fieldstrips his gun. Dean secretly turns on the GPS on Sam’s phone and Bobby asks how Dean is doing. He insists that he’s fine and Bobby notes that Dean is pissed that Sam said the same thing right before he went nuts. Bobby doesn’t believe it and points out that Dean has been through a lot, but Dean sticks by his statement.
At Stockville High School, Scott and two of his teammates on the swim team enter the locker room and shut the door behind them. They tell the team captain, Scott, that they heard something in the shower. The two teammates then attack their friends, saying they’re too hungry to care if they get in trouble.
At Sioux Falls General Hospital, Sheriff Jody Mills is in for an appendectomy. Her roommate, Madeline Harris, complains about incompetent surgeons. Their doctor, Gaines, comes in, ignores Madeline, and tells Jody that she came through fine and she should take it easy that night.
When Dean comes back with groceries, Sam and Bobby tell him about a report on the swim team attack that appears to be the result of a wild animal. When Dean says that Sam isn’t coming with him to investigate, Sam agrees and Bobby says that he can keep an eye on him.
Edgar meets Annie in the park and tells her that Edgar worked on a demolition crew. Annie says that they’re all hungry and she apologizes for the ones who ate the swim crew. Edgar tells her to get them in line per the boss’ orders, and he doesn’t want to bring the boss bad news. Annie says that she has an idea and asks Edgar for his help.
At the hospital, Dr. Gaines hears a child singing and goes into the exam room. When he offers to help, she asks if he’s a Dr. Sexy and he can cut into anyone he wants and remove any organs he wants. She tells Gaines that she wants to b a surgeon when she grows up, grabs his hand, and says she’s going to grow up now. She transforms into Gaines and then kills him.
Posing as an FBI agent, Dean checks out the locker room murder scene and spots the Leviathan’s black fluid.
Jody wakes up in the middle of the night and sees Dr. Gaines administering anesthesia to Madeline. He wheels her out and Jody manages to get out of bed and follow him.
Sam gets a call from Dean confirming that two of the swim team members are missing. He’s spotted them on a security camera heading toward Sioux Falls. While Dean talks, Lucifer toys with a hunting knife. Sam assures his brother that he’s okay and hangs up, and Lucifer says that he’s having a great day and drives the knife into the table.
Gaines takes Madeline to an organ transplant unit closed for renovations. Jody goes to the door and watches as Gaines cuts Madeline open and removes her liver, and then eats it. She staggers away and a nurse asks why she’s out of bed, and Jody collapses from the strain. When she wakes up, the nurse has her back in bed. Gaines comes in, wiping at his mouth, and Jody claims that she wanted to talk to a nurse about her stitches. The doctor tells her that she should stay in bed and the nurse gives Jody a sedative. Once they leave, Jody tries to get out of bed and find her purse.
Sam asks Lucifer why he doesn’t end the hallucination, and Lucifer explains that he has Sam exactly where he wants him. He tells Sam that it only ends when Sam can’t take it anymore and looks at the knife. Sam yells at him to shut up and Bobby comes in to find him yelling at empty air. He offers Sam a beer and says that Sam has beaten the Devil before. Sam sees Lucifer ram a poker through Bobby’s back and out his chest. The local phone rings and Bobby picks up. It’s Jody, who tells him that she knows he’s a monster hunter and that Gaines ate her roommate’s liver. Sam insists that he check it out and turns to find Lucifer cleaning the poker.
At the hospital, Edgar and the two swim team boys arrive. Gaines takes them into the renovated wing and explains that people consider the hospital a safe place and never question when patients die. He’s tied up the head nurse and the hospital administrator and explains that they can feed on as many people as they want. As the two teens take on the form of the two staff members, Edgar says that he’d like to stay but he has to visit some other local businesses on the boss’ orders, but the boss will be pleased with what Gaines has accomplished.
Sam is checking his gun when Dean pulls up and tells him that that the swim team boys are in Sioux Falls. He needs backup and Sam is the only one available.
Bobby gets Jody out of the hospital and puts her in a taxi for home. He then goes to the morgue and finds Madeline’s body, and discovers that it’s already been autopsied.
As Dean and Sam drives, Dean asks his brother how he’s doing. He suggests that they get him professional help, but Sam points out there’s nothing any doctor can do. Dean reminds him of Martin, the insane hunter and friend of the family, and warns that Sam will never be okay.
Dean arrives at Bobby and discovers that Sam isn’t there.
Sam and “Dean” pull up at what appears to be an office building. There are five people working inside and Dean warns Sam that when they go in, Sam needs to control himself. Sam says he has himself under control, but Dean says that they’re actually in an old factory. He transforms into Lucifer, who boasts that Sam'’ world is whatever he wants it to be. Sam draws his gun and shoots, but his bullets have no effect. Lucifer suggests that he shoot himself.
As Bobby examines Madeline’s corpse, Gaines comes in and asks if he can help. Bobby tries to pass as an inspector but Gaines says that he knows him from what he saw through Castiel’s eyes. Bobby hits him with a tool and then grabs his shotgun and fires a blast of silver buckshot. It has no effect and Bobby runs out of the morgue.
Dean follows Sam’s GPS to the factory and goes inside. He finds Sam while Lucifer transforms back into Dean. Sam aims at his brother and admits he can’t know for sure if Dean is real. When Lucifer taunts Sam, Sam fires at him and Dean tells him to calm down. Dean tells his brother that he’s been to Hell and he knows about torture. He explains that it feels different and takes Sam’s wounded hand, and then squeezes it and says it’s real pain. Lucifer begins to flicker in and out as Dean insists that the pain is different and so is he. Sam digs his own thumb into the wound and Dean says that Sam has to start by believing in him and working from there.
Bobby calls and tells Sam what happened at the hospital and that they should regroup at his home. As they drive back, Sam says that the hallucinations have stopped for the moment. When they arrive at the junkyard, they discover that the house has been torched. As they search the ruins, Dean calls Bobby’s phone but doesn’t get an answer. He leaves a message that he lied earlier and that he can’t handle everything that is happening.
Sam searches through the cars and Edgar confronts him. The Leviathan says that he and Dean are competent enough to warrant annihilating. Dean shoots him in the head with a shotgun without effect. Edgar throws Dean into a car, breaking his leg, and Sam knocks Edgar back. Edgar hits him with a pipe just as Dean releases a car from a crane, crushing Edgar. Dean crawls over to the unconscious Sam and then calls 911 before passing out.
When Dean and Sam wake up, they’re in am ambulance. Sam sees Lucifer, who says that he’s not going anywhere. He seizes and the EMT says they’re going to Sioux Falls General. Dean begs him to take them somewhere else and the EMT says they’ll do what he says.
At the junkyard, the black ooze flows back into Edgar’s crushed body.